Inflow Performance Relationship Wiggins, M.L
Short Description
Descripción: IPR Wiggins...
Description
SPE 25458 Generalized Inflow Performance Relationships for ThreePhase Flow
Society of Petroleum Engineers
M.L. Wiggins, U. of Oklahoma SPE Member Copyright 1993, Society of Petroleum Engineers, Inc. This paper was prepared for presentation at the Production Operations Symposium held in Oklahoma City, OK, U.S.A., March 2123, 1993. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083·3836, U.S.A. Telex, 163245 SPEUT.
ABSTRACT Generalized threephase inflow performance relationships (IPRs) for the oil and water phases are presented in this paper. These relationships yield adequate estimates of the productionpressure behavior of oil wells producing from homogeneous, bounded reservoirs during boundarydominated flow. The IPRs are empirical relationships based on linear regression analysis of simulator results and cover a wide range of reservoir fluid and rock properties. Methods to study the effects of changes in flow efficiency and to predict future performance are also presented.
single incompressible fluid and is the ratio of the producing rate to the pressure difference. However, Evinger and Muskat2,3 pointed out that a straightline relationship should not be expected when multiple phases are flowing in the reservoir. They presented theoretical calculations that showed a curved relationship between flow rate and pressure for two and threephase flow. Vogel4 later developed an empirical inflow performance relationship (IPR) for solutiongas drive reservoirs that accounted for the flow of two phases, oil and gas, in the reservoir based on computer simulation results. The resulting IPR equation is
INTRODUCTION
~ = 1  0.2 Pwf  0.8 (Pwfj2
Predicting the performance of individual oil wells is an important responsibility of the petroleum engineer. Reasonable estimates of well performance allow the engineer to determine the optimum production scheme, design production and artificial lift equipment, design stimulation treatments and forecast production for planning purposes. Each of these items is important to the efficient operation of producing wells and successful reservoir management.
qo;nax
Pr
(1)
Pr
Fetkovich5 also presented an empirical inflow performance relationship based on field data that has gained wide acceptance. His relationship, of a form similar to the empirical gas well deliverability equation proposed by Rawlins and Schellhardt6 , is
(2)
When estimating oil well performance, it is often assumed that fluid inflow is proportional to the difference between reservoir pressure and wellbore pressure. One of the first relationships to be used based on this assumption was the Productivity Index (PI). This straightline relationship can be derived from Darcy'sllaw for the steadystate flow of a
Both Vogel's and Fetkovich's relations were developed for solutiongas drive reservoirs and are widely used due to their simplicity. In an attempt to extend Vogel's approach to threephase flow, Brown7 presented a method proposed by Petrobras for determining the inflow performance of oil wells 483
2
GENERALIZED INFLOW PERFORMANCE RELATIONSHIPS FOR THREEPHASE FLOW
producing water. The method uses a constant PI for the water production and adds it to a Vogel relation for the oil production to obtain a composite inflow performance relationship. Sukarno8 proposed a method derived from computer simulation of threephase flow. This method resulted from nonlinear regression analysis of the generated simulator results and is based on the producing water cut and total liquid flow rate. The resulting relationship is a quadratic whose coefficients are functions of water cut. As of yet, no one has addressed the problem of predicting future performance or studied the effect of a skin region around the wellbore during threephase flow.
SPE 25458
zero flowing pressure. This profile can then be used to develop the analytical IPRs for the oil and water phases. Unfortunately, we do not always have reliable relative permeability or fluid property information. In this case, the analytical IPR is only of academic interest in our operations. To overcome this problem, generalized threephase IPRs similar to Vogel's were developed and are presented here. The resulting IPR equations are based on regression analysis of simulator results covering a wide range of relative permeability information, fluid property data and water saturations. Development of Simulator Results
In this paper, generalized inflow performance relationships are presented for threephase flow in bounded, homogeneous reservoirs. The proposed IPRs are compared with other threephase methods currently available. The methods presented are based on homogeneous reservoirs where gravity and capillary effects are negligible. Methods are also presented for predicting performance when reservoir conditions change from test conditions. This includes predicting future performance due to depletion and predicting performance when changes occur in the skin region near the wellbore.
To develop the generalized equations to predict inflow performance, IPR curves were generated from simulator results for four basic sets of relative permeability and fluid property data. Each set of data was used to generate simulator results from irreducible water saturation to residual oil saturation. Sixteen theoretical reservoirs were examined from initial pressure to the minimum flowing bottomhole pressure. Table 1 presents the range of reservoir properties used in the development of the generalized IPRs. Simulator results were obtained for a radial flow geometry and constant oil rate production. Maximum oil and water production rates were estimated at each stage of depletion from the simulator results at a minimum flowing bottomhole pressure of 14.7 psia. If the flowing bottomhole pressure did not reach this minimum during the simulation, the maximum rate was estimated from the production information available and then checked by rerunning the simulator.
GENERALIZED IPRs Wiggins, Russell and Jennings9 recently proposed an analytical IPR for threephase flow in bounded reservoirs. An advantage of the analytical IPR is that one can develop an IPR specific to a particular reservoir and its operating conditions. The major disadvantage, however, is that it requires knowledge of relative permeability and reservoir fluid properties and how they behave with pressure. This is not a large obstacle if relative permeability and pressurevolumetemperature data are available for the reservoir of interest, along with an idea of the average reservoir pressure and water saturation. With this information, one can develop the required mobility function profiles from the current reservoir pressure to near
Figs. 1 and 2 present typical oil and water inflow performance curves for Case 3 with an initial water saturation of 20% at several stages of depletion. These curves have the same characteristic concave shape noticed by Vogel in his research. The curves were normalized by dividing each point of
484
SPE 25458
MICHAEL L. WIGGINS
infonnation by the maximum rate and average pressure at the stage of depletion. The resulting IPR curves are presented in Figs. 3 and 4. The individual curves are now almost indistinguishable and can be represented by a single curve. The simulator results from all cases studied were normalized in this manner.
3
Comparison with Other Methods In order to test their reliability, the generalized IPRs were compared with the threephase IPR methods of Brown and Sukarno. Brown's method was proposed by Petrobras and is based on developing a composite IPR curve. The composite curve is generated by using Vogel's IPR for the oil phase and coupling it with a straightline PI for the water phase. Sukarno's method is based on nonlinear regression analysis of simulator results. Both methods differ from the generalized threephase IPR method presented in this paper in that they couple the water and oil rates. The proposed method assumes we can treat each phase separately.
IPRs To develop the generalized threephase IPRs, the production rate ratios were regressed on the pressure ratios. A linear regression model of the fonn
(3) was used to fit the infonnation. The statistical analysis was performed using the linear regression procedure available in the SAS System lO, a general purpose software system for data analysis.
To evaluate the three methods, infonnation presented by Sukarno in his Tables 624 to 626 was selected for comparison purposes. This information was generated by Sukarno using a simulator and was not used in the development of the proposed method. It was felt that these cases would give an unbiased indication of the reliability of the proposed IPRs.
The resulting generalized IPRs are
Tables 46 present the results of this analysis. All three methods yield similar estimates of producing rates, indicating the generalized threephase IPRs yield suitable results. The maximum difference between the simulator results and the generalized IPR is 3.98% for the oil phase and 7.08% for the water phase. This analysis shows that any of the three methods appear suitable for use during boundarydominated flow; yet, the proposed method is much simpler to use without yielding any degree of reliability. Based on simplicity, the generalized IPRs are recommended for use in applying to field data.
... (4)
and
... (5)
Figs. 5 and 6 present the simulator infonnation for all cases studied with the resulting IPR equations. Statistical infonnation is presented in Tables 2 and 3. Overall, the average absolute error was 4.39% for the oil IPR and 6.18% for the water IPR indicating the generalized curves should be suitable for use over a wide range of reservoir properties if the reservoir is producing under boundarydominated flow conditions.
PERFORMANCE PREDICTIONS WHEN RESERVOIR CONDITIONS CHANGE The generalized IPRs presented in the previous section are useful in allowing the petroleum engineer to calculate the pressure and production behavior of an oil well given the necessary test infonnation. The resulting
485
GENERALIZED INFLOW PERFORMANCE RELATIONSHIPS FOR THREEPHASE FLOW
4
Eqs. 6 and 7 can be used with well test information to study the effects of changes in flow efficiency.
estimates of flowing pressure or production rates assume that there is no change in reservoir conditions from those under which the well test was made. This is fine for many situations where one desires to estimate the effect of changing the flowing pressure on the production rate, or the effect on the flowing pressure if the rate is changed.
To utilize the proposed method, one would estimate the maximum oil and water production rates from the generalized threephase IPRs (Eqs. 4 and 5) and the flow efficiency from Eq. 6 using the skin factor estimated from a transient well test. It should be noted that large errors in estimating the outer boundary radius of the reservoir results in small errors in the flow efficiency. The maximum flow rates for the oil and water phases without skin are then estimated from Eq.7.
There are times, however, when the engineer desires to estimate the pressureproduction behavior under reservoir conditions that are different from those at which the well test was conducted. The two primary conditions of interest are changes in flow efficiency and at different stages of reservoir depletion. Changes in flow efficiency are of interest when one is considering a stimulation treatment to remove damage or improve permeability near the wellbore. The effects of depletion are encountered in predicting future performance at an average reservoir pressure less than the test pressure. In this section, we will look at using test data to predict well performance when reservoir conditions have changed.
Once the maximum flow rates are determined at a flow efficiency of one, Eq. 7 can be used to predict the maximum production rates at a new flow efficiency. Inflow performance curves are then predicted for the well at the new flow efficiency by using the generalized IPRs. Table 7 presents a comparison of the proposed method to account for changes in skin during threephase flow to simulator results. The maximum production rates calculated and presented in the table are from selected test information. The resulting error between the calculated maximum rates and simulator rates includes errors in the generalized IPRs and error in the flow efficiency approximation, Eq. 6. As indicated, the proposed method does a good job of estimating the maximum flow rates for the cases studied.
Changes in Flow Efficiency Flow efficiency can be defined as the ratio of the measured production rate to the ideal production rate. The ideal production rate is that rate which would be observed at the measured well bore pressure if skin equals zero. In equation form, this reduces to T.
3
Tw
4
In
E, =
T.
InTw

3 4
SPE 25458
(6)
Predicting Future Performance
+$
If we apply the Taylor series approach proposed by Wiggins, Russell and Jennings in developing the analytical IPR, we can write the present maximum flow rate as
This definition of flow efficiency allows the ratio of the maximum production rates with and without skin to be written as
(8)
(7)
where D is related to the mobility function by
486
MICHAEL L. WIGGINS
SPE 25458
As the average reservoir pressure decreases, we see a corresponding decrease in the maximum flow rate. When the average reservoir pressure reaches zero, there is physically no flow from the reservoir. Consequently, a linear regression model with no intercept was chosen.
(9)
The resulting relationship to predict the future maximum oil rate is
The subscript p in Eq. 8 indicates present conditions. If we relate the maximum production rate at some future time to the current maximum rate, we obtain qtl,JrJU1 = Pr,£D]n,o qtl,JrJU,
5
qtl,m&x, qtl,JrJU,
vJ P : lpr
= O.15376__ 
r ]
(12)
(10)
Pr,[D]u,~
where the f subscript refers conditions.
while the relationship for water is
to future
qW,m&x1
Eq. 10 states that the ratio of the maximum production rate at some future reservoir pressure to the current maximum production rate is related to the ratios of the reservoir pressures and the mobility function terms, D. Since the mobility function terms are functions of the average reservoir pressure, Eq. 10 suggests that the production rate ratio can be written as a polynomial in the ratio of average reservoir pressures.
qw,m&xp
= 0.59245433(Pr/ ] Pr.p
(13)
The statistical information for this analysis is presented in Tables 8 and 9. The coefficient of determination for the two relationships is greater than 0.9, indicating a good fit of the information. The F test indicates that the model is adequate to describe the information while the ttest shows the coefficients are significant.
Maximum oil rate ratios versus the average pressure ratios for all the cases studied in this research are presented in Fig. 7. This information appears to follow a quadratic relationship. As indicated, there is some variation between the curves due to relative permeability and fluid property effects; however, there is no great deviation in the curves. This agrees with the information studied in developing the generalized IPR. Fig. 8 presents the same comparison information for the water phase.
To use the proposed future performance method, one would estimate the maximum production rates from the generalized IPRs (Eqs. 4 and 5). The maximum future production rates can be estimated from Eqs. 12 and 13 at the desired average reservoir pressure. New inflow performance curves at the future depletion stage can be developed by using the generalized IPR equations with the desired reservoir pressure and maximum future production rates.
The information presented in Figs. 7 and 8 was fit with a linear regression model of the form
Tables 1012 present a comparison of simulator results and future production rates predicted by the proposed future performance
(11)
487
6
GENERALIZED INFLOW PERFORMANCE RELATIONSHIPS FOR THREEPHASE FLOW
method. The results presented in these tables indicate that the error increases as we estimate further in time, however, on an absolute basis, the predictions are within reasonable engineering accuracy.
proposed methods may have limited applicability, since very few reservoirs completely satisfy the assumptions. One might speculate that the methods have merit under less stringent conditions than those under which they were developed. Examples would include: reservoirs that have very limited water influx; reservoirs that initially had no mobile water phase but began producing water due to limited water influx; large reservoirs experiencing water influx where portions of the reservoir are isolated from the influx by producing wells nearer the reservoir boundaries. Other examples might include reservoirs that are relatively thin with respect to the drainage area where gravity effects are negligible, and partially penetrating wells where there is little vertical permeability. These examples are only speculation and further research is required before the proposed methods can be extended to these situations.
The analysis suggests that care should be taken in estimating future performance over large stages of depletion as the error may increase. This error may not be significant if the absolute difference in production values are small, as indicated by several of the examples. Based on analysis of information used in developing this method, one should exercise caution in predicting future rates at reservoir pressure ratios less than 70%. While estimates at pressure ratios less than 70% may be relatively accurate, they may contain significant errors. It is recommended that initial future performance estimates be updated every six months to one year. This would progressively reduce the uncertainty in earlier estimates as depletion occurs in the reservoir.
CONCLUSIONS
APPLICABILITY
1. Generalized threephase IPRs have been presented that are suitable for use over a wide range of reservoir properties. The proposed relationships are Vogeltype IPRs that require single point estimates of oil and water production rates, flowing wellbore pressure and average reservoir pressure.
The proposed IPRs and methods presented in this research for threephase flow were developed from analysis of multiphase flow in bounded, homogeneous reservoirs where there is no external influx of fluids into the reservoir, and apply to the boundarydominated flow regime. The methods are limited by the following assumptions: 1) all reservoirs are initially at the bubble point; 2) no initial free gas phase is present; 3) a mobile water phase is present for threephase studies; 4) Darcy's law for multiphase flow applies; 5) isothermal conditions exist; 6) there is no reaction between reservoir fluids and reservoir rock; 7) no gas solubility exists in the water; 8) gravity effects are negligible; and 9) there is a fully penetrating wellbore. Strictly speaking, the methods cannot be considered correct when other types of reservoir conditions exist, and the engineer should exercise great care in utilizing the proposed methods. From
a
practical
viewpoint
SPE 25458
2. The generalized IPRs have been verified using information presented by Sukarno and by comparison to the threephase methods of Brown and Sukarno. The proposed method yielded results as reliable as these two methods while being much simpler to use. 3. A method has been presented to estimate pressureproduction behavior due to changes in flow efficiency. The method appears to yield suitable results with maximum errors between the predictions and simulator results being less than 15% for the cases studied. This error includes errors from the generalized IPR and the definition of flow efficiency.
the
488
MICHAEL L. WIGGINS
SPE 25458
4. A method has been proposed for predicting future performance that is similar in form to a Vogeltype IPR The method is suggested by the Taylor series expansion of the multiphase flow equations proposed by To the Wiggins, Russell and Jennings. author's knowledge, no one has proposed a method for predicting future performance during threephase boundarydominated flow.
3.
4. 5.
NOMENCLATURE
~ p
Pr Pwf
CIo CIo,rnax
6.
flow efficiency, dimensionless relative permeability to oil pressure, psi average reservoir pressure, psi flowing wellbore pressure, psi oil production rate, BOPD maximum oil production rate, BOPD water production rate, BWPD maximum water production rate, BWPD external boundary radius, ft wellbore radius, ft skin factor, dimensionless regression coefficient oil viscosity, cp
7.
8.
9.
REFERENCES 1.
2.
Evinger, H.H. and Muskat, M.: "Calculation of Productivity Factors for Oilgaswater Systems in the Steady State", Trans., AIME (1942) 146, 194203. Vogel, J.V.: "Inflow Performance Relationships for SolutionGas Drive Wells", JPT (Jan. 1968) 8392. Fetkovich, M.J.: "The Isochronal Testing of Oil Wells", paper SPE 4529 presented at the 1973 SPE Annual Meeting, Las Vegas, NV, Sept. 30  Oct.
3.
oil formation volume factor, RB/STB
Ef
7
Darcy, H.: Les Fontaines Publiques de la Ville de Dijon, Victor Dalmont, Paris (1856) 590594. Evinger, H.H. and Muskat, M.: "Calculation of Theoretical Productivity Factors", Trans., AIME (1942) 146, 126139.
10.
489
Rawlins, E.L. and Schellhardt, M.A: Backpressure Data on Natural Gas Wells and Their Application to Production Practices, USBM (1935) 7. Brown, KE.: The Technology of Artificial Lift Methods, PennWell Publishing Co., Tulsa, OK (1984) 4, 1835. Sukarno, P.: "Inflow Performance Relationship Curves in TwoPhase and ThreePhase Flow Conditions", Ph.D. dissertation, U. of Tulsa, Tulsa, OK (1986). Wiggins, M.L., Russell, J.E. and Jennings, J.W.: "Analytical Inflow Performance Relationships for ThreePhase Flow in Bounded Reservoirs", paper SPE 24055 presented at the 1992 Western Regional Meeting, Bakersfield, CA, Mar. 30Apr. 1. Freund, RJ. and Littell, RC.: SAS System for Regression, SAS Institute, Cary, NC (1986).
Table 2. SAS Statistics for Oil IPR
Table 1. Reservoir Properties
Property
Case 2
Case 3
Case 4
CaseS
Porosity
0.18
0.12
0.20
0.24
15.0md
1O.0md
l00.0md
5O.0md
Permeability
DEP VARIABLE: QORATI ANALYSIS OF VARIANCE SOURCE
Height
25 ft
10ft
10ft
25ft
Temperature
150°F
175° F
200° F
200° F
Initial Pressure
2500 psi
3500 psi
1500 psi
2600 psi
Oil Gravity
25.0° API
45.0° API
15.0° API
35.0° API
Gas Gravity
0.6
0.7
0.6
0.7
30.0%
15.0%
18.0%
Water Solids
12.0%
Residual Oil Saturation
0.35
0.10
0.45
0.05
Irreducible Water Saturation
0.20
0.10
0.30
0.50
Critical Gas Saturation
0.050
0.000
0.025
0.075
Drainage Radius
1085 ft
506 ft
506ft
l085ft
WeUbore Radius
0.328ft
0.328 ft
0.328ft
0.328ft
HODEL ERROR U TOTAL
OF
2 160.09582759 80.04791379 408 0.26264508 0.0006437379 410 160.35847267
VARIABLE PRAT PRAT2
PRAT PRAT2
1 1
PARAMETER ESTIMATE
0.0001
PARAMETER STANDARD ESTIMATE ERROR 0.519167 0.008038153 0.481092 0.01012434
DF 1 1
T FOR HO: PARAMETER&O 64.588 47.518
PROB>ITI 0.0001 0.0001
Test Information:
F VALUE
PROB>F
124348.602
0.0001
PARAMETER ESTIMATES
OF
PROB>F
Table 4. Comparison of Proposed IPR to Other Methods Using Information in Sukamo's Table 624
ROOT MSE 0.02537199 RSQUARE 0.9984 DEP MEAN 0.564403 ADJ RSQ 0.9984 C.V. 4.49537 NOTE: NO INTERCEPT TERM IS USED. RSQUARE IS REDEFINED.
VARIABLE
F VALUE 141748.766
PARAMETER ESTIMATES
ANALYSIS OF VARIANCE MEAN SQUARE
2 144.14973559 72.07486780 408 0.20745539 0.0005084691 410 144.35719098
ROOT MSE 0.02254926 RSQUARE 0.9986 DEP MEAN 0.526888 ADJ RSQ 0.9986 C.V. 4.2797 NOTE: NO INTERCEPT TERM IS USED. RSQUARE IS REDEFINED.
DEP VARIABLE: QWRATI SUM OF SQUARES
MEAN SQUARE
SUM OF SQUARES
DF
MODEL ERROR U TOTAL
Table 3. SAS Statistics for Water IPR
SOURCE
SPE 25458
GENERALIZED INFLOW PERFORMANCE RELATIONSHIPS FOR THREEPHASE FLOW
8
STANDARD ERROR
T FOR HO: PARAMETERO
PROB>ITI
0.7222350.009044375 0.284777 0.01139171
79.855 24.999
0.0001 0.0001
fr,~i
Simulator
Wiggins S",BOPD 2252 65.48 105.45 142.44 176.44 207.46 235.50 260.56 282.62 310.13
2100
So,BOPD 176.31
Sw,BWPD 50.16
Sukarno S",BOPD 23.21 66.52
Brown S",BOPD 22.82 65.94 10554 141.38 173.20 200.71 223.59 241.46 253.89 264.46
fwf,fsi 1995 1785 1575 1365 1155 945 735 525 315 0
S2:BOPD 23.06 66.10 105.88 142.66 176.31 207.oI 234.45 259.00 279.34 301.77 Simulator
Wiggins
Sukarno
Brown
fwf,~i
SW, BWPD 5.91 17.54 28.85 39.73 50.16 60.01 69.18 77.46 84.64 92.67
9w,BWPD
Sw,BWPD 6.02 17.65 28.89 39.71 50.06 59.90 69.18 77.85 85.86 96.50
9w , BWPD
1995 1785 1575 1365 1155 945 735 525 315 0
490
fwf,fsi 1155
5.51 17.47 28.89 39.75 50.06 59.81 69.02 77.67 85.77 96.89
10650
143.14 176.44 206.41 233.05 256.35 276.31 300.00
6.47 18.71 29.94 40.11 49.14 56.94 63.43 68.50 72.03 75.03
MICHAEL L. WIGGINS
SPE 25458
9
Table 5. Comparison of Proposed IPR to Other Methods
Table 6. Comparison of Proposed IPR to Other Methods
Using Information in Sukamo's Table 625
Using Information in Sukamo's Table 626
Test Information:
Test Information: pwf, psi 1463 Simulator pwf,psi
F
23021.859
0.0001
ROOT MSE 0.04021352 RSQUARE 0.9949 DEP MEAN 0.4476028 ADJ RSQ 0.9949 C.V. 8.984198 NOTE: NO INTERCEPT TERM IS USED. RSQUARE IS REDEFINED. PARAMETER ESTIMATES
Case 3, 50% Initial Water Saturation Test
So
Skin 2 +5 +20
Skin 2 +5 +20
pwf,psi 1047
902 465
?wf,psi 1047
902 465
Pr,psi 2716 2886 2003
p"psi 2716 2886 2003
BOPD 200.00 100.00 25.00
VARIABLE
Simulator
l'Tedkted
qo.max, BOPD
qo,max, BOPD
ence,
(5=0)
(5=0)
200.03 220.95 117.36
191.28 222.39 118.15
BOPD 8.75 1.44 o.SO
Simulator
Predkted
Differ
Test
qw,max, qw,max,
Sw,
BWPD
BWPD
ence,
BWPD 183.19 82.60 25.75
(5=0)
(5=0)
177.78 191.55 122.39
175.20 183.69 121.71
BWPD 2.58 7.86 0.68
PRAT PRAT2
Percent Error 4.38 0.65 0.68
DifferPercent Error 1.45 4.10 0.55
491
DF
PARAMETER ESTIMATE
STANDARD ERROR
T FOR HO: PARAMETERO
PROB>ITI
0.15376309 0.83516299
0.01896232 0.02247023
8.109 37.168
0.0001 0.0001
10
GENERALIZED INFLOW PERFORMANCE RELATIONSIDPS FOR THREEPHASE FLOW
SPE 25458
Table 10. Comparison of Simulator Results and Future Performance Predictions Using Proposed Relationship for Case 2 Table 9. SAS Statistics for Water Future Performance Relationship Test Information: 30% Initial Water Saturation pr.p, psi 90,max,p' BOPD 2375 96.34 DEP VARIABLE: QWRAT ANALYSIS OF VARIANCE SOURCE MODEL ERROR U TOTAL
DF
SUM OF SQUARES
MEAN SQUARE
F VALUE
PROB>F
2 234 236
81. 58898652 0.31074416 81.89973068
40.79449326 0.001327966
30719.520
0.0001
pr,f,psi 1886 1447 633
ROOT MSE 0.03644127 RSQUARE 0.9962 DEP MEAN 0.4943643 ADJ RSQ 0.9962 C.V. 7.371341 NOTE: NO INTERCEPT TERM IS USED. RSQUARE IS REDEFINED.
pr,f, psi 1886 1447 633
9w,max,p, BWPD 0.63
Simulator 90,max,f, BOPD 56.17 29.02 5.86
Calculated qo,max,l, BOPD 62.50 38.89 9.66
DiUerence
Simulator
Calculated
Difference
qw. max,(,
qW,max,f,
BWPD 0.46 0.36 0.16
BWPD 0.44 0.31 0.12
BOPD ~.33
9.87 3.81
Percent Difference % 11.28 34.04 ~.99
BWPD 0.02 0.04 0.04
Percent DiHerence % 4.31 12.58 27.05
PARAMETER ESTIMATES
VARIABLE PRAT PRAT2
DF
PARAMETER ESTIMATE
STANDARD ERROR
T FOR HO: PARAMETERaO
PROB>ITI
0.59245433 0.36479178
0.01718355 0.0203624
34.478 17.915
0.0001 0.0001
Test Information: 40% Initial Water Saturation pr.p, psi 90,max,po BOPD 2428 76.47 Simulator
Difference
BOPD 47.73 1754 2.36
Calculated qo,max,l, BOPD 54.52 25.30 3.94
Simulator
Calculated
Difference
qW,max,(,
qw,max,f,
BWPD 6.82 4.21 1.24
BWPD 7.20 4.13 1.09
qo,max,f,
pr,f, psi 2031 1321 420
pr,f, psi 2031 1321 420
pr,f,psi 2671 1790 549
pr,f, psi 2671 1790 549
Calculated
Difference
BOPD 300.60 146.93 2151
BOPD 17.17 8.91 3.56
Simulator
Calculated
DiUerence
qw,max,{,
qW,max,(,
BWPD 40.03 24.37 6.57
BWPD 37.46 22.27 5.61
qo,max,(,
BWPD 2.58 2.10 0.96
Test Information: 50% Initial Water Saturation pr,p' psi 9o,max,po BOPD 3364 264.73 Simulator qo,max,f,
pr,f' psi 2945 1900 445
BOPD 227.87 107.09 11.66
pr,f, psi 2945 1900 445
Simulator qW,max,f, BWPD 196.23 114.92 23.11
Difference
Calculated
DiUerence
BOPD 22.79 13.57 2,41
qw,rnax,f,
BWPD 181.96 102.81 19.32
BWPD 14.26 12.11 3.79
Percent Difference % 5.40 5.72 14.20
pr,f, psi 1155 926 507
Percent Difference % 6.43 8.61 14.59
pr,f, psi 1155 926 507
BWPD C.38 0.08 0.16
Percent Difference %
5.64 2.01 12.48
Difference
Simulator
Calculated qw,max,l, BWPD 0.82 0.61 0.29
DiUerence
BWPD 0.89 0.72 0.38
BOPD 1.71 2.71 1.24
BWPD 0.07 0.11 0.09
Calculated
BOPD 0.69 C.25
596
BOPD 26.64 18.66 7.27 Calculated qw,max,f, BWPD 14.42 11.10 5.65
Difference
pr,f, psi 1244 1022 596
Simulator qw,max,f, BWPD 14.85 1150 5.65
Difference
qo,max,f,
C.35
BWPD 0.43 039 0.01
Percent Difference % 4.57 11.49 15.50 Percent DiUerence % 8.39 15.05 23.63
9w,max,p, BWPD 18.06
Simulator qo,max,l, BOPD 27.33 18.41 6.92
pr,f,psi 1244 1022
492
9w,max,,,, BWPD 1.04
Calculated qo,max,f, BOPD 39.16 26.26 9.24
Test Information: 50% Initial Water Saturation pr,p, psi 9o,max,,,, BOPD 1421 34.39
Percent Difference % 10.00 12.69 20.64 Percent Difference % 7.27 10.54 16.41
~7.51
Simulator qo,ma",f, BOPD 37.45 23.56 7.99
qw,rr.ax,{,
9w,max,p, BWPD 227,96
Calculated qo,max,l, BOPD 205.08 93.52 9.25
~.79
7.76 1.59
Test Information: 40% Initial Water Saturation Pr.p, psi 90,max,,,, BOPD 1333 5151
9w,max,p, BWPD 49.44
Simulator qo,max,l, BOPD 317.77 155.83 25.07
BOPD
Percent DiHerence % 14.23 44.23
Table 12. Comparison of Simulator Results and Future Performance Predictions Using Proposed Relationship for Case 4
Table 11. Comparison of Simulator Results and Future Performance Predictions Using Proposed Relationship for Case 3 Test Information: 20% Initial Water Saturation pr,p' psi 90,max,p' BOPD 3172 416.54
9w,max,,,, BWPD 9.59
Percent Difference % 2.52 1.34 5.12 Percent DiHerence % 2.93 3.43 0.12
SPE 25458
MICHAEL L. WIGGINS
1000
2000
3000
11
4000
pwf,psia Fig. 2 Water inflow performance curves for Case 3, 20% Swi, at several stages of depletion generated from simulator results.
Fig. 1. Oil inflow performance curves for Case 3, 20% Swi, at several stages of depletion generated from simulator results.
1.0 1.0
0 0
0
% 0.8
0
°cP 0
0.8
0
00
00
cDo
/1 ~
l;l
'b
0.6
t5%
...... 0
0" 0.4
0 0
0.6
a:t
~ ......
DC
eg.
0
0 00 0
0 [JJ
~ 0" 0.4
,
Bo 0
Cu::J
& 0.2
0.0
0.2
0.4
0.6
0.8
QJ
c
\
0.0
IC
0.2
~
0.0 0.0
1.0
0.2
0.4
0.6
0.8
pwf/pr
pwf/pr
Fig. 4. Water IPR curves for Case 3, 20% Swi.
Fig. 3. OilIPR curves for Case 3, 20% Swi.
493
1.0
1.0
1.0 •
0.6
1;l
t
~
"
~
"
S
0.4
0.4
0.2
0.2
qw / qwmax  1.0000  0.722235 (pwf/pr) 0.284m (pwf/prl"2
qo/qomax 1.0000  0519167 (Pwf/pr)  0.481092 (pwf/prl"2
O'O+~_r~r~,_~_,~~
0.0 0.0
0.4
0.2
0.6
0.8
1.0
0.0
0.2
pwf/pr
0.6
0.8
1.0
• 

Simulator Results Pmposed Relation
•
Simulator Results Proposed Relation
0.8
y  0.15376309 x + D.83516299 >
View more...
Comments